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Application guide:
Street: with a few careful cuts with a lathe or sharp knife, bump stops can be made to have a truly linear spring rate, emulating the OEM stops used on BMW and Porsches. Compare the OE BMW bump (green) to a linearized FCM 46mm (blue). Our force ramps perfectly linearly, even better than the BMW! This linear behavior prevents the typical harshness associated with 'hitting the bump stops,' giving a more supple ride and excellent predictability.
- 90-97 - factory stops are between 200 to 240 lb/in. If you do not wish to increase spring rates but want less roll and better transitional response, use one of the 58mm options. We recommend red or white for mostly street driving, blue for a dual-purpose car.
- 99-05 - since the factory stops are between 90-100 lb/in, we have found very good results with the softer options, including cutting the 76mm red or white down to about 57mm.
- Honda Civic - the 76mm stops are slightly shorter than factory. Use these are replacement to your OE bump stops instead of cutting them down. Choose stiffer rear stops to add oversteer.
Race (autocross): in situations like Stock class where the primary spring cannot be changed, these new bump stop options allow you greater flexibility in tuning the suspension behavior.
- E-Stock 90-97, R-package - the OE rubber stop is about 240 lb/in. If you have a large front bar, you may benefit from the 58mm blue in the rear, and either red or white up front to mimize steady-state understeer.
- C-Stock 99-05, Hard S/MSM - the OE MCU rates are softer than the NA, which allows more body roll. Mazda made the shock lengths longer on the NBs to compensate so using the stiffest 58mm and 76mm stops is not advised. For those using a 1" solid or Racing Beat 1 1/8" tubular front bar, we suggest the 58mm red in the front and 58mm white for the rear. Those using the BIG Racing Beat 1 1/4" front bar should also use the 58mm red front and white rear but the front can be trimmed 10-15mm or more to reduce bump stop engagement and allow more rotation when cornering. CAUTION: we suggest adding a 3mm packer for every 9mm of material removed. So cutting 15mm of bump stop means adding 5-6mm of packer. Experiment and see if there is any tire rubbing at full cornering - we want to limit this and also prevent the shock from bottoming if the bump stop is too short. Contact us with further questions.This bump stop tuning is useful to reduce/eliminate steady-state understeer often resulting from a larger front bar.
- Street Touring/Prepared/Modified/etc.: while a sufficient primary steel spring is needed to handle the bulk of the weight transfer, there is considerable evidence that using a bump stop in conjuction with a slightly softer primary steel spring will provide more grip by reducing contact patch load variation. The more even the contact patch load can be made, the more consistent grip the tires can produce and that wins races! These tuning techniques have been used successfully in Winston Cup and Indycar to name a few.
- We believe the best benefit will be to utilizing either a rather stiff bump stop with moderately stiff primary spring, or a linearized bump stop with a very stiff primary spring. The first case will help to maximize grip; the second case will give more effective suspension travel since you are not afraid of using the linearized bump stop and can lower the vehicle more, or use a softer primary spring than without the bump stop.
NOTE1: The SCCA Solo2 rules, 2007 edition, section 13.5.D. indicates that bump stops may be changed provided they do not contact the shock body any earlier than stock. Please ensure your setup meets the requirements of this rule as we are not responsible for any violations due to improper length for your particular shock and bump stop combination.
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